The present application includes a computer program listing appendix on compact disc. Two duplicate compact discs are provided herewith. Each compact disc contains an ASCII text file of the computer program listing as follows:
Filename: 554xe2x80x94999671 Computer Program Listing.txt
Size: 48,936 bytes
Date Created: Jan. 17, 2001
The computer program listing appendix is hereby expressly incorporated by reference in the present application.
The invention generally relates to three-dimensional prototypes constructed from stacked layers, and more particularly to a method, computer file format, and configuration for making improved rapid prototypes that provide useful information pertaining to a three-dimensional object or system.
Rapid prototyping techniques have been developed for producing three-dimensional models based on stored data describing an object. U.S. Pat. No. 4,575,030 to Hull describes a technique known as stereolithography, whereby a three-dimensional prototype is built by stacking successive thin layers of a solidified curable fluid medium. In a particular embodiment, an ultra-violet light beam movable under computer control in an X-Y plane is used to cure a surface layer of a fluid bath, and a platform in the bath is then moved incrementally in a Z direction to allow curing of the next layer, and so on. It is common practice for computer-aided design (CAD) drawing files to be converted to an STL file format for stereolithography. The STL file format defines the three-dimensional external surface of an object by specifying a set of many flat planar faces known as xe2x80x9cfacetsxe2x80x9d and the outward pointing normals associated with the facets.
Another technique is described in U.S. Pat. No. 4,940,412 to Blumenthal. This patent teaches a method of manufacturing three-dimensional anatomic models by using a series of tomographic section images as masks between a light source and a liquid photosensitive polymer. The body part section and a grid for registering the body part with actual tissue are represented as transparent regions of the opaque mask.
European Patent Publication No. 0 535 984 A1 discloses a rapid prototyping method designed to improve on the essentially homogeneous color and texture exhibited by prototypes formed by the previously mentioned techniques. In one embodiment, a photocolorable agent is added to the photohardenable liquid composition that is not activated by the curing radiation wavelength. After each layer is formed by irradiating the liquid, a color differing from that of the hardened layer is incorporated at chosen regions of the layer by selectively exposing the chosen regions to radiation which does activate the photocolorable agent. In another embodiment, a dye is deposited on chosen regions of each layer to achieve color difference. In yet another embodiment, a photoresponsive agent capable of altering tactile characteristics by controlling the degree of crosslinking in the polymer is added to the photohardenable liquid composition for selective activation by irradiation.
U.S. Pat. No. 5,596,504 to Tata et al. is concerned generally with algorithms for improved processing of an input STL model data file in an automated stereolithography system.
An inexpensive alternative to stereolithography is described in U.S. Pat. No. 5,663,883 to Thomas et al. According to this method, a three-dimensional object represented by an STL file is electronically decomposed into a plurality of thick layers, which are then electronically sliced into cross-sectional slices the thickness of a sheet of construction material. The slices are cut from sheets of construction material in a pattern which permits simultaneous construction of several thick layers by stacking a plurality of sheets. The thick layers are then assembled to form the completed prototype.
U.S. Pat. No. 5,705,117 to O""Connor et al. relates to a method of combining inserts of a non-photopolymer material into a rapid prototype produced by stereolithography to provide a functioning prototype. According to the method, an STL file is modified to include cavities for the inserts, and is then divided into a series of subpart STL files used to develop individual sections of the part. The individual sections of the part are separated at locations where the inserts are to be positioned. The photo-curing process is paused to allow a non-photopolymer insert to be manually positioned on one section of the developing part each time a section is formed. The subpart STL files provide various alignment structures to align the individual sections relative to the support platform.
A method for making a medical model of a body part based on digital image information, such as that provided by a computer tomography scanner, is disclosed in U.S. Pat. No. 5,768,134 to Swaelens et al. The method is characterized by the incorporation of additional digital information corresponding to a functional element into the digital image information describing the body part, whereby the functional element is realized in the produced model. For example, the method can be used for the preparation of tooth implants, wherein the model serves as a template for the implant and the functional element is an opening or notch at the location where drilling is required.
U.S. Pat. No. 5,779,833 to Cawley et al. discloses a rapid prototyping technique involving contoured layers cut from sheets of material. The layers, which represent cross-sections of a three-dimensional object, are stacked, laminated, and secured to each other to form the object. Ceramic material sheets can be used, along with a second type of sheet made of a fugitive material, such as an organic material that burns out during firing or green tape made from inorganic powder that is converted to a loose powder during firing. The fugitive material is cut into layers representing voids in the object and stacked with the ceramic layers, thereby allowing complex geometries to be achieved.
Finally, U.S. Pat. No. 5,818,718 to Thomas et al. is directed to a rapid prototype modeling system that includes software for electronically decomposing a discrete part represented by an STL file into electronic layers using a paradigm characterized by a higher than zero order fit with respect to the surface of the part.
Therefore, it is an object of the present invention to provide an inexpensive rapid informational prototype of an object or system that represents information describing aspects of the object or system apart from merely its shape.
It is another object of the present invention to provide a rapid informational prototype in the form of a rapid colored prototype wherein information is represented by differently colored regions of the prototype.
It is a further object of the present invention to provide a rapid informational prototype that has added tabs for easier assembly and manipulation of the prototype.
It is a further object of the present invention to provide a method for making a rapid informational prototype as mentioned above in a straightforward manner.
It is a further object of the present invention to provide a computer data file format for electronically representing a rapid informational prototype formed in accordance with the present invention.
It is a further object of the present invention to provide a computer data file format for a rapid informational prototype that is supplemental to the existing STL file format.
The present invention generally involves a method of manufacturing an informational prototype of a three-dimensional object or a system having three or more dimensions. Pursuant to the method of the present invention, a series of slices through the object or system are defined by an ordinal number, overall contour information for describing shape of the slice in an X-Y plane, slice thickness information for describing thickness of the slice in a Z direction, and slice image information for providing useful information other than the overall contour information, preferably through color images. Useful information might include, for sake of example, thermal gradients, stress contours, internal elements or time dependent changes. The method further involves cutting or otherwise extracting a plurality of layers corresponding to the defined slices from stock material, such as transparent plastic, and applying corresponding slice image information to the layers. The image information can be applied to the layers either before or after they are extracted from surrounding stock material. Finally, the layers are stacked based on the ordinal numbers of the corresponding slices to form the informational prototype. In a preferred method, a tab is added to the contour information of each slice to facilitate manipulation of the individual layers as well as the completed informational prototype.
A data file format according to the present invention for storing a representation of a rapid informational prototype in an information medium generally comprises a file header for identifying the data file, a body segment for registering a plurality slice images with a plurality of slices taken through the object or system, and a plurality of slice segments for indicating an overall contour and a thickness for each of the slices. In accordance with the invention, each of the slice images indicates information other than the overall contour of the slice registered therewith.
Informational prototypes formed in accordance with the present invention are relatively inexpensive to produce and are helpful in visualizing aspects of the object or system prototyped beyond external shape.